Moderately cool environment with rain and wind increases cold strain and energy expenditure via carbohydrate oxidation during running exercise.

Background: Outdoor exercise often proceeds despite rain and wind in cool conditions. The aim of this study was to investigate the effects of rain with wind on physiological responses during running exercise at 70% V̇O2max in cool conditions.

Methods: Eleven healthy men exercised on a treadmill at 70% V̇O2max intensity for 60 min under conditions of 10 mm/h rain and 3 m/sec wind (RW) or not (CON) at 10°C in a climatic chamber able to simulate various temperature, humidity, rain, and wind conditions. Body temperature, expired air, and blood samples were measured at rest and exercise.

Results: Rectal temperature, mean weighted skin temperature, and thermal sensation were all significantly lower in RW than in CON during exercise (all P<0.05). Oxygen uptake was significantly higher in RW than in CON during exercise (all P<0.05). Participants' rating of perceived exertion was significantly higher in RW than in CON at 50 and 60 min (P<0.05). Respiratory exchange ratio was significantly higher in RW than in CON at 10, 20, and 40 min. Plasma lactate concentration and plasma norepinephrine levels were significantly higher in RW than in CON during exercise (both P<0.05).

Conclusions: Rain with wind intensified body heat loss, and energy expenditure and carbohydrate oxidation increased as the body cooled. These conditions may decrease exercise performance.